During the initial Bulgarian advance, the Greek Army had not finished its concentration but once the direction of the advance was clear and it became evident that the Bulgarian Fourth Army was seriously engaged in the struggle with the Serbians the Greek Headquarters decided to go on the offensive. For that purpose, the Greeks had 8 infantry divisions and a cavalry brigade, almost their entire army. On 19 June, they advanced with two divisions (6 regiments) on a wide front against Kukush where the Bulgarian 2nd Infantry Brigade of the 3rd Division (two regiments) had fortified its positions. The fighting was heavy but the Bulgarians managed to hold the advance temporarily which convinced the Greek Headquarters to throw even more forces in the fight and outflank the Bulgarians. By 21 June the 2/3 Brigade could not cope with the crushing numerical superiority of its opponents and the arriving reinforcements from the Serres Brigade failed to avert the defeat. This forced the Bulgarians to retreat. The situation in the other sectors of the Second Army also deteriorated rapidly. Parts of the 3/3 Brigade were defeated at Kalinovo by the Greek 10th division and the 1/10 Brigade, supported by parts of the Drama Brigade, was defeated at Lachanas by the Greek 1st and 6th divisions. After the defeat at the Battle of Kilkis-Lahanas the Bulgarians retired to the north. On the right wing of the Second Army the 3/3 Infantry Brigade had dug in south of Dojran in an attempt to hold the Greek 10th Division. The Bulgarian Command order the 2/6 Infantry Brigade to reinforce the positions but the Greeks pressed two more divisions in the fight and once again compelled the Bulgarians to retreat on 23 June. The Second Army was now given the task to protect the Dojran-Strumitsa road and the Rupel Gorge that were vital for the rear of the Bulgarian 4th Army. For that purpose the army was divided in two – the 3/3 and 2/6 infantry brigades under the commander of the 6th Bdin Division were to defend the first direction and the Serres, Drama, 2/3 and 1/10 brigades under the commander of the 3rd Division were to guard the Gorge. The 11th Infantry Division was left to guard the Aegean coast between the Struma and the Mesta. The Greek Army divided its forces accordingly one group consisting of the 2nd, 3rd, 4th, 5th, 10th divisions